OBJECTIVES: Recent studies have shown an excess risk of asthma for cleaners, but it is not clear which cleaning-related exposures induce or aggravate asthma. METHODS: Risk factors for asthma were studied among indoor cleaners participating in the Spanish part of the European Community Respiratory Health Survey in 1992. In 1998, 78 of the 91 subjects reporting cleaning-related jobs in 1992 were identified. Of these, 67 indoor cleaners were interviewed by telephone about their cleaning activities and their use of cleaning products in 1992. These data were related to asthma prevalence in 1992, and the cleaners were compared with a reference group of office workers. RESULTS: Asthma prevalence was 1.7 times higher [95% confidence interval (95% CI) 1.1-2.6] among the cleaners than among the referents, being highest among private home cleaners (3.3, 95% CI 1.9-5.8). The prevalence of housedust mite sensitization amounted to 28% for the home cleaners and was significantly (P<0.01) higher than for other indoor cleaners (3%), but similar to the corresponding prevalence of office workers (22%). More than half of the cleaners reported work-related respiratory symptoms. The asthma risk of the home cleaners was mainly associated with kitchen cleaning and furniture polishing, with the use of oven sprays and polishes. CONCLUSIONS: The asthma risk of Spanish cleaners is primarily related to the cleaning of private homes. This relationship may be explained by the use of sprays and other products in kitchen cleaning and furniture polishing